In more detail
Each day's hours are clock-out minus clock-in, less unpaid breaks; the daily figures are added up for the week and multiplied by the hourly rate, with any overtime at its higher rate. Totals are usually shown both as hours and minutes (7:30) and as decimal hours (7.5), and payroll uses the decimal form: decimal = hours + minutes / 60. Some employers round punches to set increments, such as the nearest quarter-hour, which must even out over time where rules require it. Shifts that cross midnight need the date as well as the time.
Why it matters
Mixing the two notations is the most common time-card error: 7 hours 55 minutes is 7.92 hours, not 7.55. Small errors repeated every day add up to noticeable pay differences over a year.
Example
Clock in 08:47
Clock out 17:12
Unpaid break 0:30
Worked 7:55 = 7.92 h
At $20 an hour that day pays $158.33. Writing it as 7.55 hours would pay for only 7 hours 33 minutes.